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Boating with the TIDE

Boating with the TIDE

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Boating with the TIDE

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  1. Boating with the TIDE ITEA Conference Salt Lake City Dr. Brad Christensen Berea College

  2. Why boats? • Fun • Interesting • Many activities that can be done in the classroom • Absolutely critical for a world economy • Full of opportunities for Constraints, Optimization, and Predictive Analysis

  3. Basic boat dimensions • LOA length over all • LWL length water line • Beam width • Beam WL usually 90%-95% of beam • Draft boat hull below the water line • Freeboard boat hull above the water line • Displacement amount of water pushed aside

  4. Displacement vs Planing hulls • Displacement hulls • Usually rounded • Upswept buttock lines aft • Can be heavy • Push water out of the way and then allow it to flow back behind the boat • Planing hulls • Usually more flat or square • Straight buttock lines aft • Lightweight • Designed to skim over the water

  5. Displacement • (Beam WL X draft) X mid section coefficient = midsection displacement • (LWL X Midsection displacement) X Prismatic Coefficient = displacement in cubic feet • 1 cubic foot of water weighs about 64 pounds

  6. Floatation • How much weight will it take to sink another inch? • Water plane area • Multiply water line length (LWL) by water line beam times prismatic coefficient (.76 for a standard hull) • Water is 5.34 pounds for 1 sq. ft. 1 inch deep • Light fine ended sailboats .68 • Heavy, full ended sailboats .71 • Fine ended power boats .74 • Full ended planing boats .80

  7. Center of Buoyancy • Usually about 55% of LWL from bow • Can be as much as 65% for some powerboats • More accurate to make a CB calculator • Graph displacement at each section of hull • Connect the points with a fair curve • Cut out graph and balance on a knife edge • Balance point is the Center of Buoyancy

  8. Trim • Square of the water plane area and multiply by 0.35 (for square feet). Divide that number by the water line beam. • 16 ft by 2 ft kayak water plane area is 20.8 sq. ft. • 20.8 squared = 424.32 • 424.32 times 0.35 = 148.5 • 148.5 divided by 2 = 74.25 foot/pounds per inch of trim • If you placed 74 pounds one foot behind the CB, the bow would be about 1 inch above the stern

  9. Out of trim • How much out of trim is still okay? • About 1% of LWL • 1% of 16 ft (192 inches) LWL is about 2 inches

  10. How fast will she go? • How fast do you need/want to go? • 4 miles per hour rowing • 10 miles per hour sailing • 50 mph is very, very fast on water • Most skiers do about 30 mph or less • Most production powerboats operate best at 20-35 mph • Super high speed boats do between 80-120 mph • World speed record is 315 mph held by Ken Warbly of Ohio since the late 1970s

  11. Speed of a displacement hull • Theoretical Hull speed • Knots = 1.34 times square root of LWL • 1 knot = 1.15 mph • Increase LWL will increase hull speed….up to a point • Increases LWL increases wetted surface which increases drag

  12. Speed of a planing hull • Most critical factor in planing boat speed is the power to weight ratio • Accurate weight • Boat • Crew • Supplies • Fuel • diesel 7.2 lbs/gal • gasoline 6.1 lbs/gal • Fresh water • 8.4 lbs/gal

  13. Speed of a planing hull • Accurate power • Outboards power measured at prop • Inboards figure about 95% • Engines run continuously at about 60%-70% max so figure horsepower at about 60%-70% max rating • Subtract another 4%-6% for friction in the drive train

  14. Speed of a planing hull • Pounds per horsepower ratio • 5 lbs/hp 80 knots • 10 lbs/hp 60 knots • 15 lbs/hp 50 knots • 20 lbs/hp 42 knots • 25 lbs/hp 37 knots • 30 lbs/hp 33 knots • 35 lbs/hp 31 knots • 40 lbs/hp 29 knots

  15. Fuel Economy • Diesel engines • 0.055 gallons per horsepower per hour • 100 horsepower engine would use 5.5 gallons per hour • 100 horsepower drives a 2000 pound boat at about 38 mph so the boat gets 6.9 mpg • Gasoline engines • 0.1 gallons per horsepower per hour • 100 horsepower engine would use 10 gallons per hour • 100 horsepower engine drives a 2000 pound boat at about 38 mph so the boat gets 3.8 mpg

  16. Speed of a sailboat • Usually displacement hull so limited by LWL • Sail area to displacement ratio (power to weight) • Sail area divided by Displacement (in cubic feet to the 2/3 power) = SA/Disp ratio • Cruising boats 16-18 • Performance cruisers 18-20 • Racing boats 20-22 • High performance racer 22 and up • Performance multihulls 28 and up

  17. Barge Activities • Make it float • Hold a lot of weight for given size • Make it fast • Hull shape for best speed given size, weight, and power • Make it efficient • Pay for weight carried but charge for power • Ideal tank • 1 ft wide by 20 ft long, 6 inches deep • falling weight and string for power

  18. Barge Activities

  19. Sailboat activities • Running (wind astern) • Simple • Outdated • Reaching (wind abeam) • Faster • More realistic • Ideal tank • 2 ft by 10 ft by 1 ft deep • box fan on the end • 4 box fans along the side

  20. Power boat activities • Rubberband power • Paddle wheel • Simple • Slow • Above water propeller • Simple • Fast • Below water propeller • Fast • Realistic

  21. Powerboat activities • Electric • Battery • Solar • Gasoline • Model airplane engines • “Weed Eater” engines • Ideal tank (dependent on anticipated speed) • 8 ft wide by 24 ft long by 1 ft deep

  22. Boat Racing

  23. Control of model boat • Free running • String • Wire • Infrared • Pre-programmed • Radio control • 2 channels • Steering • Throttle

  24. Boat control

  25. Model boat to real boat • Build a model to ¾ inch = 1 foot scale • 1 penny weighs 25 pounds • Multiply boat speed times 4 to determine performance of actual boat

  26. Boat Building • Taped seam construction • Plywood panels cut to shape • Held together with plastic ties • Joints taped with fiberglass • Strip built • Thin strips edge glued over frames • Fiberglased inside and out • Hybrid • Plywood hull • Strip deck

  27. Small boat design class Plywood panels are cut to shape from full-scale patterns.

  28. Small boat design class Panels are taped together end to end with fiberglass cloth to provide necessary length. Waxed paper gives smooth finish.

  29. Small boat design class

  30. Small boat design class

  31. Small boat design class

  32. References • The Nature of Boats: Insight and Esoterica for the Nautically Obsessed, Dave Gerr, International Marine, Camden Maine